Added ability to upload and send media, and more fixes

Uploading and sending media are different things.
Once you have uploaded a media file, you can send
it to many users without uploading it again, since
you have a handle to the uploaded file.

Other fixes include not showing additional data
on error messages and not generating correct
code for sending bytes

tl_generator.py

@@ -282,7 +282,7 @@ def write_onsend_code(builder, arg, args, name=None):
         pass  # These are actually NOT written! Only used for flags
 
     elif 'bytes' == arg.type:
-        builder.writeln('writer.write({})'.format(name))
+        builder.writeln('writer.tgwrite_bytes({})'.format(name))
 
     elif 'date' == arg.type:  # Custom format
         builder.writeln('writer.tgwrite_date({})'.format(name))